import time
scale= 50
print("执行开始".center(scale//2,'-'))
start= time . perf_counter()
for i in range(scale+1):
    a='*'* i
    b='.'* (scale-i)
    c=(i/scale)*100
    dur=time.perf_counter()-start
    print("\r{:^3.0f}%[{}->{}]{:.2f}s".format(c,a,b,dur),end='')
    time.sleep(0.1)